Module 5 : MODERN PHYSICS
Lecture 23 : Black Body Radiation
Cosmic Microwave Background
  According to the big bang theory , the universe, at the time of creation was a very hot and dense object. Subsequently it expanded, bringing down the temperature, the present temperature of the universe isapproximately 2.7 K. As a result, the peak intensity of radiation is given by
 
$\displaystyle \lambda_{max} = \frac{0.29}{2.7}\approx 0.1\ {\rm cm}$
  The wavelength lies in the microwave region. This is known as the cosmic microwave background. The energy density at this temperature is obtained by multiplying $ \sigma T^4$ by $ 4/c$, which gives $ 4.01\times 10^{-14}$ J/m $ ^3$.
   
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